As this type of pliers, there is a known pair of pliers proposed by the present applicant (Patent Document 1). In this pair of pliers, as shown in FIG. 11, respective opposed faces of jaw portions 33 of a pair of pinching arms 31 and 32 crossed in a shape of X are provided with longitudinal pinching teeth 34, front pinching teeth 35, and back pinching teeth 36. The longitudinal pinching teeth 34 pinch a peripheral face of a screw head 41 along a screw shaft. For example, as shown in FIG. 12, if a screw fastened face 42 is horizontal, the longitudinal pinching teeth 34 are used to pinch the peripheral face of the screw head 41 in a state in which the whole pliers are oriented vertically. The front pinching teeth 35 and the back pinching teeth 36 are used to pinch the screw head 41 or the like in a state in which the whole pliers are oriented horizontally, if the screw fastened face 42 is horizontal.
The longitudinal pinching teeth 34 are made up of three sawtooth-shaped streak teeth 34a and diagonal oblique sides 34b connected to the streak teeth 34a in a shape of a mountain range. The front pinching teeth 35 are disposed on opposite sides of the oblique sides 34b and the opposed front pinching teeth 35 mate with each other to thereby define a limit of closing of the pinching arms 31 and 32. The front pinching teeth 35 and the back pinching teeth 36 are respectively provided with streak teeth 35a and 36a orthogonal to the streak teeth 34a described above.
A similar pair of pliers is disclosed in Patent Document 2 in which a pair of pinching arms has a reverse crossing structure similar to a crossing form of a pair of scissors for a left-handed person to thereby suppress backlash of the pinching arms in loosening a screw.